Not Applicable.
Not Applicable.
The present invention relates generally to communication systems, and more particularly, to wireless communication systems.
There are many types of communication systems for transferring data from one node to another node. One type of communication system known as a fixed wireless system includes a series of remote subscriber units having a fixed location. The remote subscriber units are associated with a cell or sector that is served by a base station. In general, each base station communicates through the air with the remote subscriber units within the cell or sector served by the base station. The wireless link from the base station to the remote subscriber units is referred to as the downlink and the link from a remote subscriber unit to its serving base station is referred to as the uplink.
To increase the data throughput of the network, conventional fixed-wireless systems typically re-use available frequency resources in a cellular manner. In such a system, however, co-channel interference due to frequency re-use becomes a significant limitation in the overall system data throughput. To reduce re-use co-channel interference, some known fixed wireless systems attempt to control the power of the signal transmitted by the base station (downlink) or by the remote subscriber units (uplink) to limit excessive transmitting power. However, typical power control algorithms are directed to continuous data traffic, such as circuit-switched voice. Due to its bursty nature, packet-based data traffic presents additional co-channel interference reduction challenges. For example, it is relatively difficult to continuously monitor the link quality and adjust the transmitting power for packet data traffic.
In addition, wireless data services such as wireless Internet, multimedia, and other wireless data communications can generate broadband packet data traffic that demands a relatively high data throughput from a wireless access network. Further, for certain applications, such as Internet browsing, a large downlink data throughput is more desirable than uplink throughput.
It would, therefore, be desirable to provide a power control technique that minimizes co-channel interference when downloading data in a bursty fixed wireless network.
The present invention provides a fixed wireless network that controls the power of signals transmitted by a base station to remote subscriber units for minimizing co-channel interference. Although the invention is primarily shown and described in conjunction with a fixed wireless communication system, it is understood that the invention is applicable to other wireless communication systems in which increasing the downlink data capacity is desired.
In one aspect of the invention, a fixed wireless communication system includes a plurality of service areas or cells, each of which is served by a base station that transmits signals to remote subscriber units within the service area. The base station transmits signals at a respective one of a plurality of power levels based upon the destination remote subscriber unit. More particularly, each remote subscriber unit is assigned to one of a plurality of groups, each having a group pathloss interval. The pathloss range for the service area is apportioned into the groups such that each group has a pathloss range within the overall pathloss range for the service area. Based upon its pathloss range, each group is associated with a particular transmit power level.
In one embodiment, the pathloss for the service area is linearly apportioned by dividing the total service area pathloss by an interval value so as to determine the number of groups in the service area. The remote subscriber units are assigned to one of the groups based upon the pathloss of the remote subscriber unit, which has a fixed location in relation to the base station.
In a further aspect of the invention, a method for controlling signal transmission power levels in a fixed wireless communication system includes determining a pathloss range for a service area and apportioning the pathloss range into groups, each having an associated pathloss range interval. The method further includes assigning remote subscriber units within the service area to one of the groups based upon the pathloss of the remote subscriber unit to the base station and assigning a transmit power level to each of the groups based upon the group pathloss interval. Data for a destination remote subscriber unit is then transmitted at a respective power level based upon the group to which the destination remote subscriber unit is assigned.